1. Field of the Invention
The present invention relates generally to intraluminal prostheses and methods for their use. More particularly, the present invention relates to intraluminal grafts and stents having oblique ends to reduce stenosis, and methods for the treatment of defective body lumens using such prostheses.
Vascular diseases amenable to treatment by the devices and methods of the present invention include both occlusive diseases and aneurysms. Occlusive diseases are characterized by the build-up of stenotic materials in the affected blood vessel, resulting in partial or total occlusion of the blood vessel lumen.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending distally into one or both of the iliac arteries.
The use of stents is gaining widespread acceptance in the treatment of occlusive diseases. Usually, a stenotic lesion is treated by balloon angioplasty with the simultaneous or subsequent placement of a stent to maintain vessel patency. While holding great promise as an improvement over angioplasty alone, the use of stents can have drawbacks. Of particular concern to the present invention, stents can themselves provide initiation sites for hyperplasia, particularly at each end where the edge of the stent is exposed to the blood vessel lumen. It would therefore be desirable to provide improved stent designs which would lessen problems associated with post-placement hyperplasia.
Aortic aneurysms are most commonly treated in open surgical procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of a usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and requires experienced surgeons and well equipped surgical facilities. Even with the best surgeons and equipment, however, patients being treated frequently are elderly and weakened from cardiovascular and other diseases, reducing the number of eligible patients. Even for eligible patients prior to rupture, conventional aneurysm repair has a relatively high mortality rate, usually from 3% to 10%. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery takes several weeks, and often requires a lengthy hospital stay.
In order to overcome some or all of these drawbacks, endovascular graft placement for the treatment of aneurysms has been proposed. Although very promising, many of the proposed methods and apparatus suffer from other problems. In particular, hyperplasia (excessive cellular proliferation) may occur in blood vessels at the regions adjacent to the ends of an intraluminal graft, stent, or other prosthesis. Such hyperplasia within the lumen of a blood vessel is potentially stenotic, and therefore compromises the therapeutic value of the intraluminal graft.
For these reasons, it would be desirable to provide improved intraluminal prostheses, including both grafts and stents, and methods for treating aneurysms, stenosis, and other conditions using such prostheses. It would be particularly desirable if the prostheses would provide the therapeutic value of existing grafts and stents, but would reduce the stenotic effect of the hyperplasia which generally occurs at the ends of existing structures. It would be further desirable if such prostheses could be inserted and positioned using conventional delivery catheters and methods.
2. Description of the Background Art
Vascular graft prostheses having oblique ends for replacement or bypassing of diseased blood vessels in open surgical procedures are described in U.S. Pat. Nos. 5,127,919 and 4,441,215. An intraluminal graft having a helical end is disclosed in U.S. Pat. No. 5,037,427. Intraluminal grafts having ends normal to the lumen are disclosed in U.S. Pat. Nos. 5,282,860; 5,211,658; 5,167,614; 5,156,620; 4,877,030; and 4,830,003.
Other designs for intraluminal prostheses are described in copending application Ser. Nos. 08/255,681 and 08/290,021, the full disclosures of which are incorporated herein by reference.
The present invention provides intraluminal prostheses, including both grafts and stents, for the treatment of disease conditions, particularly aneurysms. The intraluminal prostheses provide a decreased risk of luminal occlusion (as discussed below) and comprise a tubular member which is insertable into a body lumen in a small diameter configuration and which can be expanded within the body lumen to an expanded mode. At least one of the ends of the tubular member will have a terminal edge which is disposed at least partially at an oblique angle relative to the lumen of the tubular member.
The intraluminal prostheses may be self-expanding, expandable by the application of a radially outward internal force, or a combination thereof. Self-expanding prostheses are typically delivered to a target location within the body lumen in a radially compressed configuration, e.g. within a tube or other constraining structure. Such self-expanding prostheses may be deployed by first positioning at the target location and subsequently releasing the constraint to permit the prosthesis to expand an anchor within the lumen. Expandable prostheses are delivered to the target location without the need for constraint and are deployed by internal radial expansion, usually by inflating a balloon or other expandable structure within the lumen of the prosthesis. Self-expanding prostheses will preferably be constructed from resilient materials, such as spring stainless steel, shape memory alloys, shape memory plastics, elastic (resilient) plastics, and the like. Expandable prostheses will be preferably constructed from malleable materials such as stainless steels, titanium alloys, tantalum alloys, plastics, and the like. Prostheses have both self-expanding and expandable properties and may be constructed from combinations of these materials.
The intraluminal prostheses of the present invention are suitable for a wide variety of therapeutic uses, including stenting of the ureter, urethra, biliary tract, and the like. The devices and methods will also be useful for the creation of temporary or long term lumens, such as the formation of fistulas. The present invention will find its greatest use, however, in the placement of endovascular grafts into blood vessels for the treatment of abdominal and other aneurysms, vascular stenoses, and the like.
The present intraluminal prostheses provide significant advantages over previously proposed designs, particularly for vascular uses. Any hyperplasia which occurs at the oblique ends of the present invention will occupy an oblique region of the lumen in which the present prosthesis is positioned. Although the total volume of hyperplasia may be the same or greater, the resulting occlusion is reduced, (i.e. effective residual lumen area is increased) because the hyperplasia is distributed axially over the surface of the lumen. In contrast, conventional prostheses having terminal edges perpendicular to the lumen axis will cause a greater degree of occlusion since the opposed regions of hyperplasia are axially aligned across a perpendicular cross section of the lumen. Thus the stenoses of the present intraluminal prostheses are effectively reduced over previous intraluminal prostheses designs.
An additional advantage results from the ability to orient the prosthesis to avoid blocking branch vessel(s). It will be appreciated that a prosthesis having normal ends must be axially positioned to one side of a branch artery to avoid partial or complete occlusion. This limitation can be a significant problem where there is a limited area of blood vessel wall for anchoring the prosthesis. The oblique end of the present invention allows the prosthesis to be anchored beyond the branch vessel without occlusions by properly turning the prosthesis to avoid blockage. This is a particular benefit in the treatment of aortic aneurysms where the graft may be oriented to avoid the renal arteries.
The present invention also provides graft prostheses which comprise a tubular member as described above and a liner covering at least a part of the inside of the lumen and/or the outside surface of the member. The tubular member is usually perforate, and the liner provides a barrier which permits use as a vascular graft for the treatment of aneurysms. Preferably, the ends of the liner are aligned with or parallel to the terminal edges of the tubular frame. The liner is tied, spot welded, or otherwise secured to the tubular member in such a way that the liner can radially expand with the member. Exemplary liner structures suitable for use with the present invention are described in copending application Ser. No. 08/255,681.
The present invention further comprises methods for treatment of disease conditions, particularly aneurysms and stenoses. The treatment method comprises inserting the intraluminal prosthesis into the body lumen while the prosthesis is in its reduced diameter configuration. The prosthesis is positioned within the diseased portion of the lumen, and is expanded to the expanded configuration, either resiliently or by application of an internal expansion force. The expanded prosthesis includes at least one end which is oblique to the lumen of the prosthesis, whereby any hyperplasia which occurs along the line defined by the oblique end will be axially distributed so that effective occlusion of the body lumen is reduced.